Tuberculosis Testing: When to Get Tested for TB - GoodRx (2024)

Tuberculosis (TB) is a disease that has been around for centuries. There are better treatments available now than 3,000 years ago, but people today are still dying from the disease. In 2020, 1.5 million people around the world died from TB.

The tricky thing about TB is that it can hide out in the body for years without causing any symptoms. So some people don’t even know they have it. But the best time to treat TB is before it causes active disease. So we’ll explain how to know if you need a TB test.

What is tuberculosis?

The bacteria Mycobacterium tuberculosis causes tuberculosis. This bacteria can infect any part of the body, but it’s most common in the lungs. It spreads when a person with active TB coughs or sneezes.

There are two forms of TB: active and latent. In the active form, the bacteria causes you to have symptoms and feel sick. A person with active TB can transmit the bacteria to other people. In the latent (dormant) form, the bacteria is inside the body, but the immune system contains it. So it doesn’t cause any symptoms or illness.

Who is at risk of getting tuberculosis?

Tuberculosis happens in every part of the world. But it’s more common in some places, such as parts of Africa and Asia. While TB can infect anyone, there are some situations that increase the risk of active disease:

• Being in close contact with someone who has active TB

• Living in or immigrating from parts of the world with high rates of TB

• Being a young child

• Living with HIV

• Experiencing homelessness

• Living or working in a hospital, correctional facility, nursing home, or shelter

• Having a medical condition that affects the immune system

Who needs to test for TB?

There are two main reasons to test for TB:

1. You have symptoms of active TB.

   See Also

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2. You are at risk for having latent TB.

Let’s go through these reasons in a little more detail.

You should be tested if you have any symptoms of active TB. These include:

• Cough that lasts more than 3 weeks

• Blood in the sputum

• Weight loss without trying

• Fever, chills, and night sweats

Most people with TB have the latent form. So they won’t feel sick. But sometimes, with age or changes in health, the immune system becomes a little weaker. The bacteria may then begin to grow and cause active TB.

Even if you don’t have symptoms of active TB, there are still some reasons to test for TB to see if you have the latent form. You should be tested if:

• A test is required for your school, work, or travel

• You’re starting a medication that could weaken your immune system

• You have or develop a condition that could affect your immune system

• You have any of the risk factors for TB that are listed above

Do you still need to be tested if you had the TB vaccine?

Bacille Calmette-Guérin (BCG) is the only vaccine for TB. It’s not used much in the U.S. But infants get it in some countries where there are higher rates of TB. The vaccine can help prevent TB in babies and young children. But it doesn’t protect older children or adults very well. So even if you had a BCG vaccine as a child, you should still be tested for latent TB.

Do you need to be tested for TB during pregnancy?

If you have risk factors for TB and you’re pregnant, this is a good time to be tested. Your immune system can be affected during pregnancy and after delivery. That could put you at higher risk of active TB if the bacteria is in your body. Infants are also at higher risk of getting sick with TB, so it’s important that the people around them are healthy.

TB tests are safe to do when you’re pregnant. If the test is positive, but there are no signs of active disease, treatment can often wait until after the baby is born. But if there are signs of active TB, it’s better to start treatment during pregnancy.

How does a tuberculosis test work?

There are two types of tests that look for TB in the body: a skin test and a blood test. Both of them check for evidence that your immune system has been in contact with the TB bacteria. So both TB tests look for active disease and latent infections.

1. Tuberculosis skin test

Another name for the TB skin test is a PPD test. For this test, a healthcare professional injects a small amount of a special protein under the skin of your forearm. If you’ve been in contact with the TB bacteria, the skin will react to the protein by developing swelling under the skin in 48 to 72 hours.

TB skin tests are inexpensive and readily available. But they do require two visits with a healthcare professional. The first visit is for the injection, and the second visit is to figure out if there was a positive reaction.

2. Tuberculosis blood test

A TB blood test also looks for evidence of an immune response to TB bacteria. This test only requires one visit. And the results are usually ready in 24 to 48 hours. But the blood test may be more expensive or harder to find.

The blood test is better for people who have received a TB vaccine in the past. This is because the skin test can show a positive reading in some people who had the vaccine, even if they don’t have a TB infection. It’s also better for people who may not be able to return for a second visit.

What to do if the results come back positive

A positive TB test means that you have the TB bacteria in your body. But your healthcare provider will need to run more tests to find out if the TB is active or latent. They’ll ask you more questions about your medical history and symptoms. They’ll also perform a physical exam to look for signs of a TB infection. Finally, they’ll do a chest X-ray to see if there are signs of active TB in the lungs.

If the history, physical exam, or chest X-ray suggest active TB, the next step is a series of sputum samples. Sometimes you can do this with a deep cough into a specimen cup. But in other cases it’s hard to get a good sample with a cough, so you may need a bronchoscopy. A bronchoscope is a device that looks into the airways of the lungs.

Treatment for latent TB infection uses 1 to 2 drugs for 3 to 9 months. Active tuberculosis requires treatment with 2 to 4 drugs over 4 to 9 months. For both latent and active infections, your healthcare provider will help to choose the combination of medications that is most effective for you.

It’s important to work as a team with your healthcare providers to complete the entire treatment. And people who have been in close contact with someone with active TB should also be tested.